This primarily refers to maintaing common action sequences, terms, units, layout, colour, typography and so on, within an application. The interface should offer no surprises, so users should not have to guess why something has happened or what should be done next.

If actions are orderly, predictable and describable by a few rules, they will be easy to learn and retain. For example, error messages should always appear on screen in the same position and format. Consistency therefore should be a blanket theme for the entire interface. Despite this non-game designs demand predictable behaviour, whereas the random events occurring in most games are designed as a challenge. However consistency is a strong determinant of success of systems, and should extend throughout the game map and indeed across application programs.

Users will come to a system armed with a variety of prejudices and stereotypes. These impressions may be formed in conjunction with earlier computer systems or they may simply be from life in general. To the HCI designer these expectations should be a consideration. Obviously is impossible to predict what all users will expect from a system, but certain areas have become standard in recent years, hence, spreading familiarity.

If a certain button or icon always performs a certain task - it should always perform this task in the application domain.